What’s up? Night sky for May 2011

Stargazers looking at the sky

May will be a great month for planet watchers, with four bright planets visible to the east before dawn.

THIS WILL BE A FANTASTIC MONTH for planet watchers, with a series of attractive close groupings in the eastern morning sky. Mercury, Venus, Mars and Jupiter will be in the same part of the sky, and you’ll get the chance to watch their shifting positions as the month progresses.

Why do they appear to move around relative to each other? It’s because they’re on independent orbits about the Sun and travelling at different speeds. The Earth is moving around the Sun too, and our shifting perspective adds to the apparent sky motion. In fact, the word ‘planet’ comes from the Greek, and means ‘wandering star’.

Except where indicated, all of the phenomena described here can be seen with the unaided eye. And unless otherwise specified, dates and times are for the Australian Eastern Standard Time zone, and sky directions are from the point of view of an observer in the Southern Hemisphere.

May 1

There’ll be a fantastic planetary get-together in this morning’s eastern sky. First, Jupiter and Mars will be just less than half a degree (roughly one Moon width) apart. Jupiter will be the brighter, whitish-coloured one on the right, with ruddy-coloured Mars on the left. Also present will be the crescent Moon … below and to the left of the planet Venus, and left of the planet Mercury, and above and to the left of the Jupiter-Mars pair. It’ll be a fantastic sight! Why not try taking a photo of it?

May 3

New Moon occurs today at 3:51pm Sydney time (06:51 Universal Time).

The Moon

The Moon is always a popular target for stargazers.

May 7

The planets Venus and Mercury will be side-by-side in this morning’s eastern sky, only 1.5 degrees apart (about three Moon widths).

May 8

Mercury, the innermost planet, will be at its greatest angular distance (27 degrees) from the Sun this morning.

May 11

It is First Quarter Moon today at 5:33am Sydney time (May 10, 20:33 Universal Time). The period around First Quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains throw nice shadows, making it easier to get that 3D effect.

Also this evening, the Moon will appear close to Regulus, the brightest star in the constellation Leo. The amazing thing about Regulus is that, although to the naked eye it appears to be one star, in reality it is composed of four stars grouped into two pairs, all gravitationally bound to each other! This sort of thing is not too uncommon, as many other stars are members of double, triple or quadruple systems too.

May 12

Another planetary grouping in this morning’s eastern sky, with Venus only half a degree (one Moon width) to the right of Jupiter, and Mercury about three Moon widths above and to the left.

May 14

This evening the almost-full Moon will be perched about 7 degrees above the planet Saturn.

May 15

Tonight the Moon, just a smidge short of being full, will be only 1.5 degrees (about three Moon widths) above and to the right of the star Spica, the brightest star in the constellation Virgo. Spica is a blue giant star, 7.4 times as big as our Sun, and the 15th-brightest star in our night sky. Also today, the Moon will be at the closest point in its orbit around the Earth, called perigee. The distance between the two bodies will be 362,133 kilometres.

Diagram showing planets in the morning sky

Four planets are visible in the morning sky. This diagram shows the view on May 16.

May 16

Yet another arrangement of planets in our morning sky to the east. Venus will be about three Moon widths below and to the left of Mercury, about eight Moon widths below and to the right of Jupiter, and about six Moon widths above ruddy-coloured Mars.

May 17

Full Moon occurs today at 8:09pm Sydney time (11:09 Universal Time).

May 18

Tonight, look for the Moon about four degrees (eight Moon widths) below and to the left of Antares. Antares is a red supergiant star, the brightest star in the constellation Leo and the 16th-brightest star in our night sky. And get this—Antares is 800 times the diameter of our Sun, so you can see why they call it a supergiant!

May 22-31

Venus, Mars and Mercury will do a dance with each other in the morning sky over the final week of the month, in close proximity to one another. Have a look each morning and see how the arrangement has changed.

May 25

It is Last Quarter Moon today at 3:52am Sydney time (May 24, 18:52 Universal Time).

May 27

Today the Moon will reach the farthest point in its orbit, apogee, at a distance from Earth of 405,003 kilometres.

May 30-31

The crescent Moon will join the Mars, Venus, Mercury triplet in the morning sky.

And here’s Melbourne Planetarium‘s fabulous astronomer, Tanya Hill, to show us what the month’s sky will look like in motion:

If you have any questions or comments on the night sky, we’d be happy to answer them. Please use the Feedback Form below. Happy stargazing!

Images courtesy IAU / TWAN / Babak A. Tafreshi / Andreas O. Jaunsen / IYA2009 / Galileoscope.

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